The present invention relates to a fuel exchange apparatus used for fuel exchange in a nuclear reactor in a nuclear power station.
In the nuclear reactor of a nuclear power station, fuel, specifically, fuel assemblies in a nuclear reactor are exchanged in annual inspection being performed during shutdown of the nuclear reactor. In the fuel exchange operation, spent fuel assemblies are taken out of the nuclear reactor and transferred to a spent fuel storage pool and new fuel assemblies are loaded in the nuclear reactor. Further, the fuel assemblies in the core are shuffled, that is, repositioned so that the fuel assemblies can be evenly burned.
This fuel exchange operation is performed by using a fuel exchange apparatus. The fuel exchange apparatus has a traveling carriage being moved horizontally in one direction, a traversing carriage being moved horizontally on the traveling carriage in a direction orthogonal to the direction in which the traveling carriage moves, and a fuel holding unit attached to the traversing carriage. The fuel exchange apparatus is disposed so that it can move across the spent fuel storage pool and nuclear reactor well pool disposed above the nuclear reactor.
The fuel holding unit has an telescopic tube, a holding tool, and a lifter. The telescopic tube is provided so that when a fuel assembly held by the holding tool is moved in the water in the spent fuel storage pool and nuclear reactor well pool, the fuel assembly can withstand the resistance of the water. The telescopic tube is formed by telescopically assembling a plurality of metal pipes, called masts, having different diameters, so that the telescopic tube can extend and contract. The holding tool is structured so that it can hold and release a fuel assembly, and attached at a lower end of the telescopic tube. The lifter has wire ropes as linear members for suspending and supporting, and also includes winch as winding means for winding and running out the wire ropes. The winch is provided with the traversing carriage. The wire ropes are used to suspend and support the holding tool from the traversing carriage. When the wire ropes are wound or run out by the winches, the holding tool is raised or lowered, and the telescopic tube is contracted or extended in synchronization with the raising motion or the lowering motion of the holding tool.
The exchange and shuffle of the fuel assemblies in which the fuel exchange apparatus is used are performed as described above, by positioning the holding tool of the fuel holding unit at a necessary position by moving both the traveling carriage and traversing carriage. The operation for taking out the fuel assemblies from the nuclear reactor is performed, as described below in detail. First, a lid of the nuclear reactor is opened, and the fuel exchange apparatus is moved to a position above the nuclear reactor well pool by moving the traveling carriage. The holding tool of the fuel holding unit is then positioned right above a spent fuel assembly to be taken out by moving the traveling carriage and traversing carriage. The telescopic tube is extended at that position by running out the wire ropes from the winch, and the spent fuel assembly in the core is held by the holding tool. The telescopic tube is contracted by winding the wire ropes by the winch and the spent fuel assembly is taken out from the nuclear reactor. The fuel exchange apparatus holding the spent fuel assembly is moved from above the nuclear reactor well pool to above the spent fuel assembly storage pool. The spent fuel assembly is positioned right above any of the storage racks in the spent fuel assembly storage pool by moving the traveling carriage and traversing carriage. The telescopic tube is extended again at that position to lower and the spent fuel assembly is deposited in the storage rack. The spent fuel assembly is released from the holding tool and stored in the storage rack.
The shuffle of fuel assemblies is performed as described bellow in detail. The holding tool of the fuel holding unit is positioned right above a fuel assembly to be repositioned by moving the traveling carriage and traversing carriage. The telescopic tube is extended at that position and the fuel assembly in the core is held by the holding tool. The telescopic tube is then contracted and the fuel assembly is taken out from the loaded position. After the fuel assembly is positioned right above a destination position at which to load the fuel assembly by moving the traveling carriage and traversing carriage, the telescopic tube is extended again at that position to lower and the fuel assembly in deposited in the destination position in the core. The fuel assembly is released from the holding tool and loaded at the destination position.
Examples of this type of fuel exchange apparatus are disclosed in, for example, Japanese Patent Laid-open No. 2006-84178, Japanese Patent Laid-open No. 2004-245728, Japanese Patent Laid-open No. 2002-71879, Japanese Patent Laid-open No. 2002-82193 and Japanese Patent Laid-open No. 2000-19289.